In many projection units which include a preformed glass reflector and projection lamp (e.g. tungsten halogen) therein, the lamp is returned in alignment within the reflector by employing a suitable cement (e.g. sauereisen) within the reflector and about the lamp's sealed end. Examples of such arrangements are shown in U.S. Pat. Nos. 3,314,331 (Wiley) and 3,639,750 (Anthonijsz). Use of cement or a similar permanent-type bonding agent prohibits separation of the lamp and reflector in the event that replacement of either of these components is necessary. In many cases, it is only the incandescent lamp which fails and needs replacement. The aforementioned permanent bond between lamp and glass reflector was believed necessary in order to assure the essential, precise alignment between said components and between these members and other elements (e.g. film gate, projection lens) within the overall system. Alignment between reflector and lamp was usually achieved using a precisioned instrument whereupon the assembled unit was ready for insertion within a respective socket-holder arrangement, such as shown in U.S. Pat. No. 3,789,212 (Wagner). This latter positioning is usually accomplished by the projector's operator.
Mandatory replacement of both lamp and glass reflector therefore results in unnecessary waste of material which in turn adds appreciably to the overall cost of operating such systems.
The projection unit of U.S. Pat. No. 4,156,901 (Haraden et al.) was designed to eliminate the above undesirable requirement by providing a retention member which is removable from the rear of the reflector yet which also assures positive alignment of the unit's incandescent lamp within the reflector when said lamp is positioned therein. The retention member is secured to the lamp's sealed end and may comprise a metallic "can", a preformed component of insulative material such as ceramic, or a combination of both.
The projection unit of U.S. Pat. No. 4,219,870 (Haraden et al.) was designed as an improvement to the unit of U.S. Pat. No. 4,156,901 by providing means whereby the retention member having the lamp's sealed end therein could be removed from the front, concave reflecting portion of the glass reflector. As stated, the method of removal in U.S. Pat. No. 4,156,901 was via the rear neck (or collar) portion of the reflector. This earlier arrangement necessitated provision of a relatively large aperture (opening) in the reflector's neck portion thus reducing the total reflective surface of the reflector and, as a result, the unit's total forward output. In addition, rearward removal of the lamp in many projection systems currently available today can prove somewhat difficult due to the limited accessibility to this portion of the unit within most systems. The technique of forward (front) removal understandably overcomes the above and other, related disadvantages. In the unit defined in U.S. Pat. No. 4,219,870, a pair of retention members is utilized, one for retaining the sealed end of the lamp and aligning the lamp within the glass reflector while the other, an external clamping member, is slidably positioned within a pair of opposing, exterior slots in the glass reflector's neck portion and functions by slidably engaging upstanding tabs located on the portions of the boxlike first retention member which protrude from the rear of the reflector a necessary distance.
The present invention represents yet another improvement of the variety above by providing a projection unit which permits use of a relatively small opening in the glass reflector to accommodate the unit's lamp and first retention member, both of which are removable from the front of the reflector, and which utilizes a relatively small, compact resilient second retention member pivotally located on the first member and capable of being inserted through the reflector's rear opening during initial positioning of the lamp's first retention member component and thereafter being pivoted to engage a surface of the reflector and secure (or lock) the component in position.
It is believed therefore that a projection unit which provides the above improvements, as well as those defined in greater detail below, constitutes a significant advancement in the art.